fakuivan
New Member
Describe your setup
The unit in question is a Must PH1800 (or PV1800, not sure) 4KVA rebranded by Renogen as a PHI-4KW. I'm monitoring it using Home Assistant with [this Modbus to MQTT relay](https://github.com/fakuivan/docker-must-homeassistant). The link points to my fork, I made some minor modifications.
This inverter is connected to a bank of 4s AGM batteries totaling 48V nominal. The battery bank has been replaced at the begginging of this year, and it has been used pretty sparsely, not more than 50 cycles at no more than 50% DOD.
The solar array is composed of 2s4p 72 cell panels. Voc is around 75 in winter and 65 in summer.
Here are some pictures of the unit, including some specs.
Describe the behaviour you're seeing
The charge controller seems to be resetting quite frequently with no obvious pattern. This has been happening for about two years now, the behaviour is very prevalent in winter if the load is less than 400W, in summer since the ACs are on full blast most of the time the sun is up the charge controller rarely enters this state of resetting around every 5 minutes.
Here's a view into the state of the inverter. The curve `Inversor_Warning1` with a value of 1024 means the inverter is firing the warning "PV charger communication error". When this happens little charge controller icon in the LCD screen of the inverter disappears.
Edit: note that the PV voltage goes to zero from time to time. This isn't what's really happening, the inverter just writes zeros to the Modbus registers that belong to the charge controller on this failed state. You can see that the moments when PV voltage goes to zero correlate perfectly with when warning 1024 is registered.
Why do you think this is happening?
At some point in the past the 2s4p array was configured as 3s3p, and it could have been the case that at some point Voc exceeded the 160V max input the charger is rated for. I took a look inside the unit and there's no disconnect relay present for the solar input, the terminals go straight into the input filtering caps and the switching elements. Maybe something got damaged slightly at some point resulting in this strange behaviour.
Besides this, I have no other suspicions as to why the charge controller could be behaving like it does.
What have you tried to do to fix this?
From seeing that this would repeat more frequently at times where the load was in the range of 0 to 500W, I enabled a mode where the battery woud discharge at sunset, and then charge at sunrise, proividing a more consistant load. The reasoning is that batteries show a more stable voltage at charge states closer to the nominal voltage, otherwise at the extremes (like fully charged or nearly fully discharged) the change in voltage per unit of energy provided is quite large, meaning that the charge controller would need to react more quickly to changes in AC loads and solar availability to avoid overvolting the battery.
This would _sometimes_ help avoid the unit getting into the constant resetting state, but it didn't make the issue go away, so I'm not counting it as a solution, nor do I want this to taint any other opinions in case this ends up having nothing to do with the actual problem.
What do you need help with?
1. Has anyone with a similar model ran into one of these problems before? 2. How could I debug this? 3. How can I get more information about this unit like scmenatics, service manuals or firmware? Would you recommend any specific resources? 4. What options do I have that do not involve replacing the charge controller board or replacing the unit.
The unit in question is a Must PH1800 (or PV1800, not sure) 4KVA rebranded by Renogen as a PHI-4KW. I'm monitoring it using Home Assistant with [this Modbus to MQTT relay](https://github.com/fakuivan/docker-must-homeassistant). The link points to my fork, I made some minor modifications.
This inverter is connected to a bank of 4s AGM batteries totaling 48V nominal. The battery bank has been replaced at the begginging of this year, and it has been used pretty sparsely, not more than 50 cycles at no more than 50% DOD.
The solar array is composed of 2s4p 72 cell panels. Voc is around 75 in winter and 65 in summer.
Here are some pictures of the unit, including some specs.
Describe the behaviour you're seeing
The charge controller seems to be resetting quite frequently with no obvious pattern. This has been happening for about two years now, the behaviour is very prevalent in winter if the load is less than 400W, in summer since the ACs are on full blast most of the time the sun is up the charge controller rarely enters this state of resetting around every 5 minutes.
Here's a view into the state of the inverter. The curve `Inversor_Warning1` with a value of 1024 means the inverter is firing the warning "PV charger communication error". When this happens little charge controller icon in the LCD screen of the inverter disappears.
Edit: note that the PV voltage goes to zero from time to time. This isn't what's really happening, the inverter just writes zeros to the Modbus registers that belong to the charge controller on this failed state. You can see that the moments when PV voltage goes to zero correlate perfectly with when warning 1024 is registered.
Why do you think this is happening?
At some point in the past the 2s4p array was configured as 3s3p, and it could have been the case that at some point Voc exceeded the 160V max input the charger is rated for. I took a look inside the unit and there's no disconnect relay present for the solar input, the terminals go straight into the input filtering caps and the switching elements. Maybe something got damaged slightly at some point resulting in this strange behaviour.
Besides this, I have no other suspicions as to why the charge controller could be behaving like it does.
What have you tried to do to fix this?
From seeing that this would repeat more frequently at times where the load was in the range of 0 to 500W, I enabled a mode where the battery woud discharge at sunset, and then charge at sunrise, proividing a more consistant load. The reasoning is that batteries show a more stable voltage at charge states closer to the nominal voltage, otherwise at the extremes (like fully charged or nearly fully discharged) the change in voltage per unit of energy provided is quite large, meaning that the charge controller would need to react more quickly to changes in AC loads and solar availability to avoid overvolting the battery.
This would _sometimes_ help avoid the unit getting into the constant resetting state, but it didn't make the issue go away, so I'm not counting it as a solution, nor do I want this to taint any other opinions in case this ends up having nothing to do with the actual problem.
What do you need help with?
1. Has anyone with a similar model ran into one of these problems before? 2. How could I debug this? 3. How can I get more information about this unit like scmenatics, service manuals or firmware? Would you recommend any specific resources? 4. What options do I have that do not involve replacing the charge controller board or replacing the unit.
Last edited:
